I. Field of the Invention
The present invention relates to a bucket for a power shovel.
II. Description of the Prior Art
There are many previously known buckets for power shovels of the type used for dredging, digging and the like. Many of these previously known buckets are known as "clam shell" buckets and consist of two bucket halves which are pivotally secured to each other. Each bucket half forms a scoop and, as the bucket halves pivot together, these scoops close together and form a load carrying chamber. The power shovel then moves the closed bucket with its load to the desired dumping site.
Power shovels with buckets are frequently used to remove hazardous waste and the like from the bottom of waterways. In such situations, it is desirable to remove a relatively shallow volume of earth from the bottom of the waterway since spills of hazardous material typically remain near the top of the soil.
There have been previously known buckets for power shovels, such as the bucket disclosed in my prior U.S. Pat. No. 5,029,923, which are designed to remove a relatively shallow amount of earth during a digging or trenching operation. One problem with these previously known buckets is that, as the bucket halves are moved from their open to their closed position, an amount of soil escapes from the sides of the bucket and between the bucket halves. Furthermore, the soil or earth which escapes in this fashion is frequently contaminated with hazardous waste since it represents only the outer portion of the removed soil. Consequently, overlapping trenching or digging is required in order to ensure removal of the hazardous waste.
In order to prevent the escape of the load from the bucket halves as the bucket is moved from its lowered to its raised position for dumping, it has been the previously known practice to form the bucket halves as substantially closed chambers. Consequently, with the bucket halves in their closed position and enclosing a load of contaminated soil, the closed bucket halves prevent the spillage of soil out from the top of the bucket.
One disadvantage of forming the bucket halves as closed chambers, however, is that, as the bucket is lowered into a waterway and toward the bottom of the waterway, the closed bucket halves displace water during the descent of the bucket. This displaced water creates water currents caused by the lowering of the bucket. Disadvantageously, these water currents tend to wash the soil away from the bottom of the bucket before the bucket reaches its lowered position. The soil that is washed away by the water currents, however, is oftentimes the most heavily contaminated with hazardous waste.
A still further disadvantage of these previously known buckets is that the wet soil to be moved from the bottom of the waterway tends to cling to the sides of the bucket even as the bucket is moved to its open position. This in turn increases the difficulty of cleaning the bucket and ensuring that all of the hazardous waste is removed from the bucket before the bucket is again lowered into the waterway.